b)$\ \ \ $How do you determine where the graph of $f$ is concave upward or downward?

c)$\ \ \ $How do you locate inflection points?

4.$\ \ \ $If $f(x) = \frac{x^2}{x^2 - 1}$, find (a) the intervals on which $f$ is increasing or decreasing, (b) the $x$-values of local maximum and minimum values, and (c) the intervals of concavity and inflection points. Justify each response.